Horn radiator



Samh 5 mm M. KATZIN HORN RADIATOR Filed Dec. 12, 1940 R x E m m E U 0 WA N .w I A M M Y B I ,3. W M a Patented Nov. 14, 1944 Search Room HORN RADIATOR Martin Katzin, Riverhead, N. Y., assignor to Radio Corporation of America, a corporation of Dela- Ware Application December 12, 1940, Serial No. 369,826

10 Claims.

The present invention involves ultra-short wave horn radiators and, more particularly, is directed toward means for operating a single radiator of this type to simultaneously radiate or receive signals at a plurality of different frequencies.

An object of the present invention is to provide a single horn radiator for the simultaneous or selective transmission and/or reception of separate intelligence bearing signals at different frequencies.

Another object of the present invention is the provision of means for simultaneous energization of a wave guide structure with two separate signals at different frequencies without interaction therebetween.

Still a further object of the present invention is the provision of a horn radiator, as aforesaid, in which the two signals may be spaced only moderately in the frequency spectrum or in which the frequencies may differ by a factor of two or more.

In general, in employing the present invention a rectangular tapered wave guide section is used as a horn to simultaneously, or selectively, receive or transmit a pair of signals at difierent frequencies. The energizing antennas, or pick-up means, depending upon whether the horn is used for transmission or reception, are located at the small end of the tapered wave guide section. The two signals of different frequencies are radiated or received with their polarizations crossed in order to eliminate interaction. In the case of transmission, in order to provide linearly polarized radiated waves, the electromagnetic horn or tapered wave guide may be fed with Em and H1,o waves of difierent frequencies, that is, one wave will have a vertical polarization of the electric field intensity and the other, a horizontal polarization of the electric field intensity. Both waves will, of course, have a component of magnetic force in the direction of propagation.

In the above used notation the first subscript denotes the number of half sine waves in the distribution of electric field intensity in the direction parallel to the vertical axis and at right angles to the direction of propagation, while the second subscript indicates the number of half sine waves in the distribution of field intensity in the direction parallel to the horizontal axis and at right angles to the direction of propagation. The subscript denotes that the field intensity for that wave is independent of the corresponding direction.

It will be seen, therefore, that the Ho,1 wave results in a vertically polarized radiation while the H wave results in a horizontally polarized radiation. For the H1,0 wave which results in a horizontally polarized radiation the vertical dimension of the resonant chamber which surrounds the energizing means for this wave must be larger than the critical dimension, which is determined by the operating frequency of that wave. That is, the vertical dimension of the resonant chamber must be greater than a half wavelength at the operating frequency. The horizontal dimension of the resonant chamber may be arbitrarily chosen as far as the Hm wave is concerned. Similarly, the H0,1 wave, which results in a vertically polarized radiation, requires that the horizontal dimension of the resonant chamber which surrounds the energizing means for this wave must be larger than the critical dimension. As before, this horizontal dimension is a half wavelength at the operating frequency for the vertically polarized wave. The vertical dimension of the resonating chamber may be arbitrarily chosen.

In the case of a receiving horn structure a rectangular horn is coupled to a rectangular resonating chamber containing the receiving antenna and both horizontal and vertical polarizations are received by the horn simultaneously. Then the feed chamber will contain both Ho,1 and Hm waves. If the resonating chamber is tapered down in the horizontal dimension to a value less than the critical dimension for the propagation of H0,1 waves then these waves will be suppressed beyond that point and only H1,o waves will continue on past the taper. Similarly, a tapering of the chamber in the vertical dimension down to a value below the critical dimension for the propagation of H1,0 waves will allow only Ho,1 waves to pass. If desired, a further discrimination between the two waves may be provided by the insertion of a grid of parallel wires or bars at the place where the critical dimension for the propagation of the undesired wave is attained. Furthermore, if the chamber is divided into two branches and one of the branches is tapered vertically to less than the critical dimension for the H1,o waves, while the other branch tapers horizontally to less than the critical dimension for Ho,1 waves an arrangement is obtained for separating horizontal from vertical polarization, thus allowing the simultaneous reception or transmission of both waves without interaction whether their frequencies differ only slightly or by a factor of two or more.

A further development of the present invention contemplates the insertion of a grid of parallel wires or bars in each of the two branches mentioned above. In one branch, the wires are horizontally arranged and in the other, vertically. The horizontal wires absorb horizontally polarized waves and, similarly, the Vertical waves absorb the vertically polarized waves and thus further prevent interaction between the two waves.

Further objects, features and advantages of the present invention will be more clearly understood by reference to the following detailed description, which is accompanied by a drawing in which Figure 1 illustrates in horizontal section an embodiment of the present invention; Figure 2 illustrates a modification of the form of the invention shown in Figure 1, while Figure 3 illustrates still a further modification thereof.

Figure 1 of the drawing shows an arrangement which is suitable for cases where the two frequencies to be transmitted or received differ relatively widely. Here the horn structure I is shown as being of uniform taper throughout. The antenna l I for the lower frequency is placed nearer the mouth of the horn where the crosssectional dimensions are greater than the feed antenna l2 for the higher frequency. It is preferably located a suitable distance in front of a grid of wires l4 which lie parallel to the low frequency feed antenna. The distance between the antenna II and the grid [4 is determined by considerations of impedance matching of the transmission line (not shown), by means of which the antenna II is energized or by means of which the receiver is energized. The wire grid I4 is placed at a point in the horn where the dimension of the horn at right angles to antenna H is a half wavelength, or more, of the operating frequency for antenna II. The small end of the horn is terminated in a throat connected to a suitably dimensioned resonant chamber I3 for the higher frequency. The dimension of chamber 13 in a direction at right angles to the sectioning plane is at least a half wavelength of the operating frequency of antenna l2. The space between antenna l2 and the closed end of chamber 13 is determined by the same considerations as determine the space between antenna II and grid 14.

Figure 2 shows a modification of Figure 1 which is suitable for any separation of the two desired frequencies of operation. As in the case of Figure 1, the radiating horn structure It is shown of uniform taper throughout. To the small end of horn I0 is connected a feed chamber 23 having therein an energizing antenna H. The dimension of chamber 23 at right angles to the antenna ll is at least a half wavelength at the operating frequency of antenna II. The end of feed chamber 23, remote from its connection to horn I0, is closed as far as radiation from antenna H is concerned by a grid 14 of wires parallel to the antenna I I. As in the case of Figure 1, the spacing between the antenna II to the grid M is determined by considerations of impedance matching. At the rear end of the low frequency feed chamber 23 is placed a further tapered section 20 and to the throat of this section is connected the resonant chamber l3 containing therein the second energizing antenna l2. The construction of this portion of the figure is the same as in the case of Figure 1 and will not, therefore, be further described.

Still another modification is shown in Figure 3 which is also suitable for any separation of the two operating frequencies. Here an adaptation of the double polarization feed arrangements shown in my copending. application #354,955, filed Aug. 31, 1940, is employed. To the throat of horn I0 is connected a Y-shaped section, one arm of the Y comprising resonating chamber 33 having therein the low frequency feed antenna II. The dimensions of chamber 33 are determined as described above for resonating chamber 23. The other arm of the Y comprises a tapering section 20 and a resonating chamber [3 containing the high frequency feed antenna 42. The tapering section 20 and resonating chamber 13 are the same as described with reference to the foregoing figures. In order to provide an effectively continuous wave guide for both frequencies a wire grid 34 having the wires therein parallel to the low frequency antenna is placed across the arm of the Y which leads to the resonant chamber I3. Likewise, a grid 35 of wires parallel to the high frequency antenna I2 is placed across the arm of the Y leading to antenna ll. Each of these wire grids acts effectively as a continuous conductive sheet as far as waves parallel to the wires are concerned and offer very little impedance to waves having their polarization at right angles to the direction of the wires.

In all of the embodiments heretofore described the rate of taper of the horn need not be uniform throughout but may vary as described in my prior copending application #354,954, filed August 31, 1940. In the case of Figures 2 and 3 wherein a separate tapered horn connects the high frequency feed chamber to the main horn I0, the separate portion may advantageously have a steeper rate of taper since the aperture in which it terminates is relatively small. Furthermore, the interior of horn l0 may be treated as shown in my prior copending application #363,248, filed October 29, 1940 now Patent No. 2,317,464 granted April 27, 1943, in order to assure that the horn provides equal ain for both waves.

While I have particularly shown and described several modifications of my invention, it is to be distinctly understood that my invention is not limited thereto but that improvements with in the scope of the invention may be made.

I claim:

1. Means for coupling a pair of independent transducer means to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and each forming an arm of a Y, an elongated antenna mounted transversely within each of said chambers, said antennae being adapted to operate at substantially different frequencies, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for coupling the open end of said chambers to said horn so arranged that the axis of said horn lies along the leg of said Y, and means at the junction of said chambers for preventing interaction between said antennae.

2. Means for coupling a pair of independent transducer means to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and adjacent each other, an elongated antenna mounted transversely within each of said chambers, said antennae being adapted to operate at substantially different frequencies, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for coupling the open end of said chambers to the small end of said horn, and means at the junction of said chambers with said horn for preventing interaction between said antennae.

- 3. Means for coupling a pair of independent transducer means adapted to operate at substantially different frequencies to a tapered horn antenna comprising a pair of eldngated resonant chambers each closed at one end and each forming an arm of a Y, an elongated antenna mounted transversely within each of said chambers, said antennae each being adapted to operate at the frequency of its associated transducer means, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for coupling the open end of said chambers to said horn so arranged that the axis of said horn lies along the leg of said Y and means at the junction of said chambers for preventing interaction between said antennae, the arm of the Y containing the antenna adapted to operate at the higher frequency having the same dimensions as the other arm at the junction therebetween and being tapered to smoothly transfer energy from said resonant chamber to said horn.

4. Means for coupling a pair of independent transducer means adapted to operate at substantially different frequencies to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and having their open ends adjacent one another, an elongated antenna mounted transversely within each of said chambers, said antennae each being adapted to operate at the frequency of its associated transducer means, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for forming the open end of said chambersto said horn, and means at the junction of said chambers with said horn for preventing interaction between said antennae, the junction of the chamber containing the antenna adapted to operate at the higher frequency having the same dimensions as the other chamber at the junction and being tapered to smoothly transfer energy from said resonant chamber to said horn.

5. Means for coupling a pair of independent transducer means adapted to operate at substantially different frequencies to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and having their open ends adjacent one another, an elongated antenna mounted transversely within each of said chambers, said antennae each being adapted to operate at the frequency of its associated transducer means, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for forming the open end of said chambers to said horn, and means at the junction of said chambers with said horn for preventing interaction between said antennae, the junction of the chamber containing the antenna adapted to operate at the higher frequency having the same dimensions as the other chamber at the junction and being tapered to smoothly transfer energy from said resonant chamber to said horn, and further means at said junction for preventing interaction between said antennae, said last mentioned means comprising a grid across the end of each of said chambers, each lii i'ikli bit Hunt grid being conductive only in a direction to prevent the passage of wave energy of a polarization other than that for which the antenna within such chamber is arranged.

6. Means for coupling a pair of independent transducer means adapted to operate at substantially different frequencies to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and each forming an arm of a Y, an elongated antenna mounted transversely within each of said chambers, said antennae each being adapted to operate at the frequency of its associated transducer means, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for coupling the open end of said chambers to said horn so arranged that the axis of said horn lies along the leg of said Y and means at the junction of said chambers for preventing interaction between said antennae, the arm of the Y containing the antenna adapted to operate at the higher frequency having the same dimensions as the other arm at the junction therebetween and being tapered to smoothly transfer energy from said resonant chamber to said horn, said taper being substantially steeper than that 0f said horn.

7. Means for coupling a pair of independent transducer means adapted to operate at substantially different frequencies to a tapered horn antenna comprising a pair of elongated resonant chambers each closed at one end and having their open ends adjacent one another, an elongated antenna mounted transversely within each of said chambers, said antennae each being adapted to operate at the frequency of its associated transducer means, the dimensions of each of said chambers transverse to the antenna therewithin being at least half of the operating wavelength of said antenna and means for forming the open end of said chambers to said horn and means at the junction of said chambers with said horn for preventing interaction between said antennae, the junction of the chamber containing the antenna adapted to operate at the higher frequency having the same dimensions as the other chamber at the junction and being tapered to smoothly transfer energy from said resonant chamber to said horn, said taper being substantially steeper than that of said horn.

8. Means for coupling a pair of independent transducer means adapted to operate at different frequencies to a horn antenna comprising a pair of elongated rectangular resonant chambers, each closed at one end, a linear antenna mounted tansversely within each of said chambers and mutually at right angles with respect to each other, each of said antennae coupled to one of said transducer means, the dimension of each of said chambers transverse to the antenna therewithin being at least a half of the operating wavelength of the transducer means coupled to the antenna therewithin, said chambers being arranged to form the arms of a V with their open ends adjacent and means at the junction of said chambers for coupling said chambers to the throat of said horn.

9. Means for coupling a pair of independent transducer means adapted to operate at different frequencies to a horn antenna comprising a pair of elongated rectangular resonant chambers, each closed at one end, a linear antenna mounted transversely within each of said chambers and mutually at right angles with respect to each other, each of said antennae coupled to one of said transducer means, the dimension of each of said chambers transverse to the antenna therewithin being at least a half of the operating wavelength of the transducer means coupled to the antenna therewithin, said chambers being arranged to form the arms of a V with their open ends adjacent and means at the junction of said chambers for coupling said chambers to the throat of said horn, and further means at said junction for preventing interaction between said antennae, said last mentioned means comprising a grid across the end of each of said chambers, each grid being conductive only in a direction to prevent the passage of wave energy of a polarization other than that for which the antenna within such chamber is arranged.

10. Means for coupling a pair of independent transducer means to a tapered horn antenna comprising a pair of elongated rectangular resonant chambers, each being closed at one end and forming the arms of a V with their open ends adjacent, a linear antenna mounted transversely within each of said chambers and mutually at right angles with respect to each other, each of said antennae being coupled to one of said transducer means, the dimension of each of said chambers transverse to the antenna therewithin being at least a. half of the operating wavelength of the transducer means to which said antenna is coupled, the junction between said chambers being connected tothe throat of said horn, and means at said junction for preventing interaction between said antennae, said last mentioned means comprising a grid across the end of each of said chambers, each grid being conductive only in the direction normal to the antenna within its associated chamber and being arranged to form a smooth continuation of the wall of said horn into the other of said chambers.

MARTIN KATZIN. 

